This invention relates to a rotary gas proportioning inhalator which provides accurate, variable proportioning of a plurality of pressurized gases at a high rate of flow on a demand basis, while permitting the level of one gas to be maintained at a constant or adequate level.
Practical use of the inhalator of the invention is to further the art of administering carbon dioxide, oxygen and nitrous oxide to patients suffering from psychoneurosis. Carbon dioxide therapy is also beneficial for facilitating the recovery of speech in stroke victims and as an adjunctive thereapy for allergy, drug addiction and alcoholism. Finally, carbon dioxide may be used to enhance the creative process and promote greater self-realization.
In 1929 Loevenhart, Lorenz and Waters found that 30-40% carbon dioxide in oxygen enhanced mental clarity in catatonic patients for short periods of time. In 1947, L. J. Meduna used 20-30% carbon dioxide in oxygen as a neurophysiological therapy for treating psychoneurosis without psychotherapy. Meduna theorized that carbon dioxide cures psychoneurotic conditions through repeated administration of carbon dioxide thereby increasing the threshold of stimulation of reverberating neurotic circuits and achieving homeostasis by turning positive feed back systems into negative feed back systems. In 1952, Moriarty confirmed that carbon dioxide inhalation therapy was beneficial for anxiety states, phobic reactions, character disorders, migrane, alcoholism and psychosomatic conditions such as spastic colitis. Moriarty also maintained that carbon dioxide therapy works by breaking up pathological reverberating neural circuits to allow homeostatic mechanisms to reestablish themselves. He also believed that carbon dioxide therapy facilitates the psychotherapeutic process by releasing emotional tension through emotional discharge and by enhancing the accessibility of unconscious material.
To supply the gases to the patient, Meduna used a single cylinder having a fixed ratio of gases (up to 30% carbon dioxide in oxygen) which was connected by a long hose, through a large eleven liter rebreathing bag and thence, by a short tube to a face mask. When the cylinder was opened, it flowed at a constant rate into the rebreathing bag. When the patient breathed through the face mask, the rebreathing bag contracted and expanded as it lay on the patient's chest. Disadvantages of this system included inability to vary the gas mixture, inability to mix in nitrous oxide to enhance induction, the nuisance of the rebreathing bag, the variability of the gas mixture due to increases in carbon dioxide level with exhalation, and the difficulty of cleaning the rebreathing bag after each usage.
Moriarty utilized a system having three different cylinders (carbon dioxide, oxygen and nitrous oxide), with the flow of each being regulated by a separate flow meter having a manual wheel control and a visual meter. A double Y system of connected hoses brought the gases to the rebreathing bag and thence to a face mask similar to that used by Meduna. Some disadvantages of this arrangement are that all three flow meters must be regulated simultaneously to control gas proportions, that the resulting gas proportions are not precise, and that a rebreathing bag is required.
A gas mixture proportioner for a plurality of gases is described in U.S. Pat. No. 3,515,155, to Haffner et al., in which each supply line leading from one of the gas sources to a common mixing chamber contains a plurality of metering valves of different capacities connected in parallel. Gas from the mixing chamber can be fed, for example, to a diver. By using different combinations of valve size, e.g. by closing some, the rate of flow through each line is controlled to arrive at desired proportions of gas in the mixing chamber. In this system, gases mixed in the mixing chamber are fed either directly to a reducing valve and thence to the diver, or indirectly to the diver through an accumulator tank. This system is complex and costly.
U.S. Pat. No. 3,800,830, to Etter, shows a valve for selectively metering or mixing liquids or gases via apertures in a number of disk-like valve elements. The disks are stacked and connected to a common shaft. Each disk can be rotated to an off position or to an in-between position at which one or more apertures carried in skirts attached to the disks are positioned to pass gas, from a central space adjacent to the disk to which a particular gas is supplied, to an outlet line which is coupled to a manifold. This device, while providing control by each disk of admission of an individual gas to the mixing manifold, does not provide a reserve which will accommodate high volume flow on a demand basis and does not provide interrelated control of the gas proportions in the mixture.
In the mixing valve of U.S. Pat. No. 4,156,438, to Keisow, pairs of tapered movable metering openings are carried in a metering member, each tapered opening being associated with one of two gases to be mixed. A bore on the opposite side of the tapered slot collects and mixes the output. Motion of the member in which the tapered slots are carried causes more or less of one or the other of the gases to pass through into the collector. The two gases supplied are mixed in inverse proportion to each other, i.e., the percentage of one gas can be varied from zero to 100% at the same time that the percentage of other gas is varied from 100 to 0%. However this valve is not capable of proportioning three gases upon demand, nor is it capable of maintaining constant the proportion of one gas, such as oxygen, while the proportions of the other gases are varied.
It is an object of the present invention to provide an inhalator for supplying a proportioned mixture of a plurality of gases from pressurized sources to a patient while providing a high volume of flow on demand.
It is still another object of the invention to provide an inhalator arrangement in which three different gases, such as carbon dioxide, oxygen and nitrous oxide are received from separate sources at the same pressure and are mixed, so as to provide a constant or adequate level of oxygen at all times for life support while the proportion of the other two gases are variable with one adjustment by the operator.
It is a further object of the invention to provide an inhalator which is of a suitable structure for direct application to the face of a patient.